In conventional bicycles, it is well known to provide a chain and sprocket assembly with the front sprocket of the assembly having pedal cranks for rotation about a hub near the lower mid-portion of the bicycle frame. The pedals traverse a circular path and the lever arms defined by the cranks have a constant length so that the power output or the efficiency of operation of the chain sprocket assembly is constant.
It is desirable and a need exists to increase the operational efficiency of the pedal drive means of a bicycle so that the rider can have greater power output for a given amount of effort. Any such increase will allow the bicycle to be propelled forwardly at a higher speed while maintaining full control of the bicycle and its drive means.
It is also desirable and a need exists to minimize the weight of the bicycle by making the various parts of the bicycle as light as possible without sacrificing the strength necessary to withstand the weight of the rider. Various attempts have been made to reduce the weight of the bicycle frame by proper selection of the metallic material which makes up the frame. While these have been satisfactory, there is room for improvement so long as the strength and durability of the overall bicycle structure remains sufficient to support the rider.
A prior patent in the field of bicycle drive means includes U.S. Pat. Nos. 594,980 and 4,026,571.